CREATIONIST ANATOMY AND NESTED HIERARCHIES
Comparative anatomy is the study anatomical traits across groups of organisms. Among vertebrates, for instance, you can compare skeletal systems, nervous systems, muscular systems, endocrine systems, circulatory systems, respiratory systems, immune systems, digestive systems, urinary systems, and reproductive systems. One can search for similarities and for patterns in these similarities.
A) THE CREATIONIST MODEL
In the creationist model, different groups (or “kinds”) of organisms have completely separate origins. They are not at all related. Since they are not related and their origins were completely separate events, there is no relationship which has to be observed. Different organisms (let’s use a human, a monkey, a mouse, and opossum, a reptile, an amphibian, and a fish as examples) don’t have to have anything in common. There are conceivably many ways in which fluid could be circulated or gases exchanged or actions coordinated. Organisms which are utterly unrelated could have completely unrelated structures responsible for these tasks. If these distinct organisms possessed similar structures, there is no pattern of similarity that need be consistently observed. If the same structures exist in different groups of organisms, they could be identical. If there are differences between anatomical structures, no organism need possess a simple structure from which more advanced forms could have evolved since none of the traits actually did evolve. If there is a pattern of similarity that one sees when comparing nervous systems (for example: human more similar to mouse than to an opossum), there is no reason to expect that the same pattern would be observed when examining the circulatory system. Similarities could be observed which are based on factors other than ancestry such as size or habitats. Tropical opossums could be more similar to tropical mice than tropical opossums are to non-tropical oppossums. Small reptiles could be more similar to small amphibians than they are to big reptiles.
ANYTHING COULD BE OBSERVED IF THE CREATION MODEL IS CORRECT. Since the creationist model predicts nothing, no evidence would necessarily undermine it. It is not expected, however, that an analysis of every system of the body result in the same pattern of relationships again and again and again.
KINDS SHOULD BE APPARENT: Some creationists feel that there has been some evolution within a given “kind” but not from one “kind” to another. One would expect that an analysis of the data would demonstrate this: all members of a kind should share similarities with other members of their kind which are qualitatively different from any similarities with members of other kinds.
B) THE EVOLUTIONARY MODEL
In an evolutionary model, not only are similarities expected, but a pattern of similarity is expected. If humans and monkeys evolved from a common ancestor more recently than either shared a common ancestor with any other group (mice, opossums, reptiles, fish), they should be characteristics that they share which are not found in any other group. If reptiles and mammals evolved from a common ancestor more recently than the last common ancestor that either had with amphibians, there should be characteristics that they share which are not found in any other group. The pattern of similarities observed should be consistent with the diverse members of each group and it should be consistent regardless of the system which you are using in your analysis. Among the various forms of a trait, some are expected to represent more primitive forms of the trait from which more advanced forms could have evolved.
THERE IS A PATTERN OF SIMILARITY WHICH MUST BE CONSISTENTLY OBSERVED.
the creation model is true, creationists could perform anatomical studies,
publish them in refereed scientific journals, and show why the predictions
of the creation model are supported by the data while the predictions
of the evolution model are not. They have not done so. Since Darwin's
publication, the overwhelming majority of comparative anatomists have
been evolutionists and no creationist has since Agassiz has made a significant
contribution to comparative anatomy. This means that modern creationists
must explain why the leading anatomists of the past century and a half
have been utterly mistaken in interpreting the data that they collected
since creationists are not generating a database of their own. When
the anatomical structures and physiological processes of diverse organisms
are compared, what does the data suggest? There are three clear conclusions
which are drawn from anatomical studies:
If the creation model is true, creationists could perform anatomical studies, publish them in refereed scientific journals, and show why the predictions of the creation model are supported by the data while the predictions of the evolution model are not. They have not done so. Since Darwin's publication, the overwhelming majority of comparative anatomists have been evolutionists and no creationist has since Agassiz has made a significant contribution to comparative anatomy. This means that modern creationists must explain why the leading anatomists of the past century and a half have been utterly mistaken in interpreting the data that they collected since creationists are not generating a database of their own. When the anatomical structures and physiological processes of diverse organisms are compared, what does the data suggest? There are three clear conclusions which are drawn from anatomical studies:
creationists have generated essentially no new data of their own, they
must explain these conclusions drawn from the data.
Since creationists have generated essentially no new data of their own, they must explain these conclusions drawn from the data.
…structures), and metabolism that are similar. That this is true is quite evident. Is it surprising that the biochemistry (life chemistry or metabolism) of the human is very similar to that of a rat? After all, don’t we eat the same food, drink the same water, and breathe the same air? If evolution were true, similarities in structure and metabolism would be a valuable aid in tracing evolutionary ancestries, but it is worthless as evidence for evolution. These types of similarities are predicted by both the creation and the evolution models. Such similarities are predicted by both the creation and the evolution models. Such similarities are actually the fact that creation is based upon the master plan of the Master Planner. Where similar functions were needed, the Creator used similar structures and life chemistry to perform these functions, merely modifying these structures and metabolic pathways to meet the individual requirement of each organism. Much of the morphological and genetic evidence related to homologous structures in fact directly contradicts predictions based on evolution theory.
Gish, 1978, p. 168-9
I have read enough of Duane Gish’s works to know that what Gish claims the evidence supports and what the evidence actually supports are typically blatantly different. If the above statement is correct in that “similarities in structure and metabolism” are “worthless as evidence for evolution” then it is pointless to study anatomy, physiology, genetics, or embryology in an attempt to determine whether life’s diversity appeared out of nowhere or resulted from descent with modification. Creationists are often quick to disregard entire branches of biology as being irrelevant and, perhaps not coincidentally, these creationists typically have absolutely no training in these branches of science. Biologists differ—we feel that both biological data and those who have studied this data can make valuable contributions in answering questions about the biological world.
Gish claims that one would expect a rat and a human to be similar if they eat the same food and breathe the same air. This argument is UTTERLY INADEQUATE. While it may appear to address the data to those who have not studied the data, in reality it accomplishes no such thing.
Would you expect a rat and a human to have similar respiratory systems if they breathe the same air and are made by the same God? Maybe. For now I will not pursue the observation that I give God’s creativity a bit more credit and think that God could come up with an infinite number of ways for animals which are superficially similar to breathe the same air. Do reptiles, amphibians, a few fish, and terrestrial invertebrates breathe the same air? Yes. If Gish’s argument is adequate, any organism made by the same God and breathing the same air should be similar. This is not the case. Invertebrates breathe air differently than vertebrates. Vertebrates differ among themselves: a number of teleost fish can breathe through their swim bladder. Lungfish actually possess lungs although they lack a distinct pulmonary circuit (in their circulatory system). Amphibians have lungs and a nearly distinct pulmonary circuit but their pulmonary breathing is often only a supplement to breathing through the skin. Many salamanders have lost their ancestral lungs altogether. Reptiles, thanks to ribs which attach to a sternum and a long trachea, can breathe more efficiently but they lack a diaphragm. Turtles, echinoderms, and dragonflies can breathe through their anus. Crocodilians increase respiratory ability through a hepatic-piston system. Birds and many theropod dinosaurs increase gas exchange by having their lungs actually enter their bones. In mammals, a diaphragm and a secondary palate increase respiratory capacity and allow a higher metabolism.
The fact that a rat and a human have similar respiratory systems is not as important as the PATTERN of similarities which exists. If you refer to the Respiratory Cladogram in the Intelligent Design Section, you will observe that the distribution of respiratory adaptations forms a nested hierarchy. In the creationist model, a turtle, a lungfish, a frog, an ant, and a human are all equally unrelated—they at no time shared a common ancestor—and the only explanation for similarities in their respiratory systems lies in their breathing the same air and their being made by the same Creator. In the evolutionary model, invertebrates and vertebrates evolved their respiratory systems separately and therefore have distinct sets of adaptations. The first chordates and fish evolved a system of gills whose blood vessels would be modified to service the lungs in some of their descendants. The most primitive bony fish evolved a respiratory sac from the digestive tract that became paired lungs in sarcopterygian fish. Amphibians evolved a few enhancements of these lungs but it wasn’t until the evolution of reptiles (with the trachea and incorporation of rib movement into respiration) that lungs became efficient. Mammals evolved additional modifications for increased efficiency (a diaphragm, a secondary palate). The evolutionary model predicts that groups which have descended from a common ancestor will share characteristics which are not possessed by those which did not descend from that common ancestor.
Not only does the distribution of respiratory features fit the evolutionary model rather than the creationists model, the same is true of every system of the body (refer to the other cladograms in the Intelligent Design Section). The same is true of genetic data. Gish feels that rats and humans should have similarities based on the fact that they eat the same food. Primates have a variety of diets: gorillas are strictly vegetarian, some monkeys primarily eat fruit, chimps eat an occasional raw monkey, etc. An evolutionist would predict that all primates would share features of their digestive system because they have descended from a common ancestor after the rat lineage branched off. In Gish’s model, rats and gorillas are equally unrelated to humans and, if similar diet is the cause of similar digestive systems, the digestive system of a rat should be more similar to that of a human. This is not the case. Polar bears have digestive systems more similar to black bears, tasmanian devils have digestive systems more similar to opossums, and crocodiles have digestive systems more similar to box turtles despite the fact that polar bears, tasmanian devils, and crocodiles feed primarily on meat while black bears, opossums, and box turtles are more omnivorous.
Comparative anatomy and genetics offer overwhelming evidence for the evolutionary model of life’s diversity and offer absolutely no support for the creationist model. It therefore comes as no surprise that virtually all anatomists and geneticists are evolutionists, that virtually no creationists have any formal training in comparative anatomy or genetics or have made contributions to either field, and that creationists, such as Duane Gish, may try to convince their readers that anatomy and genetics are irrelevant in addressing the biological question of evolution.
2) How do creationists respond to the nested hierarchy of anatomical traits?
Evolution does predict a nested hiearchy of traits and such traits, often depicted in cladograms (see the Anatomy Book), provide overwhelming evidence for evolution. Creationism can apparently be maintained no matter what anatomical evidence is known. Conservative literalists were just as convinced of the miraculous creation ex nihilo before comparative anatomy was studied as they were afterwards.
Does evolution make precise predictions? Can one predict that exactly 260,465,321 years ago a cynodont would have mutation allowing its maxillary and palatine bones to fuse to create a secondary palate? Does it predict that 65 million years ago a big rock fell into Mexico from space and caused the extinction of 65% of life? No. Evolution claims that populations of organisms change over time. In a similar fashion, the germ theory of disease does not predict what disease will break out in Thailand ten years from now; it simply predicts that there will be a biological agent which causes it.
Evolution does account for the nested hierarchy of anatomical features better than Remine’s “Message Theory”—ask any anatomist. Remine’s philosophical arguments depend on his guessing what God was thinking, what God was “forced” to do, and what God was “prohibited” from doing. This is not science. The creationists of the 1920s, many of them members of the Klan, frequently used arguments based on what they perceived God was thinking. I am amazed our society hasn’t learned to be more wary of such arguments as a result.
There are several possible reasons why certain animals are more similar to one another than they are to others, permitting them to be arranged into groups. Animals that live in a similar environment and eat similar food would be expected to have structural and even chemical similarities. Animals that live and move on land, for example, have a certain class of similarities based on the restrictions imposed by the natural terrain of our earth. Animals that live and swim in water have certain similarities necessary for aquatic locomotion and feeding. Animals that fly in the air have still other similarities dictated by the severe demands of flight. In the same manner, man-made machines designed to serve a common type of purpose share common features, despite their many differences. Consider the various modes of transportation designed by man. Most vehicles that run on land, from roller skates to freight trains, share a class of similarities based on wheels. Vehicles that move on water, from a canoe to a battle ship, share basic similarities based on floatation. Vehicles that fly in the air, from hang gliders to the space shuttle, have similarities that are essential to flight.
Menton stated a conclusion on anatomical data that he had not gathered. This statement would be better read as a hypothesis. In the creationist model, each kind is equally unrelated. What anatomical similarities must be present between kinds in the creationist model? None. The hypothesis stated above is that organisms in similar environments and with similar lifestyles will have similar anatomical structures. This is a good hypothesis. However, it doesn’t even begin to explain the pattern of anatomical similarities observed among organisms. Creationists would know this if they studied the anatomical data before deriving their conclusions on it.
Here are a few examples:
--There are different kinds of Old World monkeys—some are small, arboreal animals while others are larger, partially terrestrial primates which are often confused with apes (baboons and “Barbary apes” are really monkeys). If Menton’s model is true, the more larger Old World monkeys would be more similar to apes in their internal anatomy than the smaller forms. This is not observed. All Old World monkeys appear to be equally related to apes, both anatomically and genetically.
--In the creationist model, placental mammal “kinds” are as unrelated to each other as they are to all other kinds. If anatomical similarity was based on similarity in habitat, then bats would be grouped with birds (as the Bible states), whales with fish, placental “flying” squirrels with marsupial gliders, etc. This is not the case. Anatomical similarities prove that placental mammals are an actual group despite the fact that the habitat and lifestyle of many placentals has more in common with non-placental mammals than with other placentals.
--There are different groups of legless animals today (snakes, lizards, worm-lizards, and caecilians) and a few other kinds have existed in the past (e.g. some Paleozoic amphibians). Their anatomy links them to legged relatives rather than with other legless groups.
--The word “vulture” describes two different kinds of body designs. New World vultures have evolved from raptor ancestors while many Old World vultures have evolved from storks.
--Gorillas differ from humans in their diet (they are vegetarians feeding primarily on leaves) but their digestive system has much more in common with ours than do those of other omnivorous animals. Whale sharks have a great deal in common with great white sharks despite the fact that they feed only on microscopic life. Polar bears are united with black bears on the basis of anatomy despite very different habitats and diets (polar bears only eat meat while most of a black bear’s diet may be composed of insects and berries).
If Menton or any one else feels that anatomical similarities are the result of “design” for a specific environment or diet or whatever, then they should actually propose groups based on such characters and then study the similarities among their group. Any such classification scheme would instantly fall apart. While the above hypothesis is a valid hypothesis, it cannot be a conclusion; the data simply doesn’t support it.
3) Nested Hierarchies Coincide
Darwin went so far as to express the opinion that the chimpanzee was more likely than the gorilla to have been the ancestor of man.
William Jennings Bryan from Carpinter, p. 132
Conclusions of the evolutionary model can be tested. While one can conclude from certain anatomical features that chimps are most similar to humans, you can test this through other means. Darwin never dreamed of the genetic tests which could compare genetic makeup (including genes which have no role in determining the anatomical features used for anatomical conclusions) and yet his conclusion holds up quite nicely. In contrast, William Jennings Bryan never made a conclusion about the natural world which has been upheld by experimental data. Science remembers Darwin and his contribution; William Jennings Bryan is all but forgotten.